摘要:

Summary.The paper in its first part deals with the germination response, in the laboratory, of four species ofPoato variations of temperature, light and the nature of the moisture supply. The second portion deals with the same response ofP. compressato solutions of various salts used as moisture supply. The third part deals with the germination ofP. compressain the soil when all the above factors were varied. In the laboratory, alternation of temperature proved to be, generally, the most, efficient stimulant followed by light and a solution of potassium nitrate as moisture supply.P. compressaproved to be more sensitive than any of the other species considered,P. pratensisandP. nemoralisrather less so, whileP. trivialiswas almost insensible to variations of the conditions. In the soil. excess of light (sunlight) proved to be depressant. Some salts.e.gpotassium nitrate, sodium nitrate, ammonium nitrate, etc., proved to be stimulating in solution culture, while salts of lead were depressant. As a general statement these salts, found to be stimulating in solution culture. proved to be more depressant in soil than those found depressant in the solution. Lead salts in the soil produced broader, deeper coloured leafage than the controls. Nitrites had a striking physical effect in preventing the drying up of the soil.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1927.tb07071.x

出版商:Blackwell Publishing Ltd    

年代:1927

数据来源: WILEY

摘要:

Summary.1In these experiments. where susceptible scions have been grafted on to “mosaic” stock, all developed “mosaic” symptoms with one exception. Circumstances were not favourable in this particular case and it. should be regarded as giving indecisive not negative evidence. From the other cases there is satisfactory proof that, the supposed “virus” can be transmitted up the growing bine.2With the “carrier” experiments, all the known susceptible sciens, which were grafted on to the “carrier” (M 45) stock, exhibited “mosaic” symptoms. The variety M 45 must, therefore. be regarded as capable of transmitting the disease to susceptible hops, and as being a “carrier.”3There is no evidence that the process of grafting can of itself in any way induce “mosaic” symptoms to pear in healthy susceptibl

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1927.tb07072.x

出版商:Blackwell Publishing Ltd    

年代:1927

数据来源: WILEY

摘要:

Summary.It is known that grafting together portions of two different plants is sometimes followed by changes in their chemical contents owing to permeation of each by substances formed in the other.The present investigation is an attempt to determine by grafting together pieces of immune and susceptible plants whether the cause of immunity from wart disease of potatoes is carried by chemical compounds which can traverse unchanged a graft fusion layer or by those which are unable so to do.For this purpose all the eight possible types of plants have been built up by grafting together root, shoot and tuber systems from either immune or susceptible plants.In none of the experiments was the reaction of the tubers towards wart disease seen to be changed.The deduction is therefore drawn that the cause of the immunity is not carried by any compound which is able to traverse the plant.In this way the problem is considerably narrowed down, for it is now possible to eliminate many lines of attack as unlikely to be fruitful.The suggestion is put forward that the examination of the proteins from immune and susceptible varieties by immunochemical methods is the most hopeful future line of attack.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1927.tb07073.x

出版商:Blackwell Publishing Ltd    

年代:1927

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1927.tb07074.x

出版商:Blackwell Publishing Ltd    

年代:1927

数据来源: WILEY

摘要:

Summary.1In the field two aspects of the “Lanarkshire Straw‐berry Disease” are apparent, namely, the devastationen masseof the strawberry beds. and the diseased condition of individual plants.2Soil conditions as a whole are unfavourable, and this tells against the development of an extensive and healthy root system.3The roots are weak and lax. consequent on the excessive stiffness of the soil. This renders them liable to fungal attack.4Roots of all kinds were found to be penetrated by fungal hyphae. and to have hyphae associated with them.5Eighteen separate extractions of fungi were made, and on twelve occasions a species ofPythiumwas the only fungus obtained.6When inoculated into pots in which strawberry plants had been grown under sterile conditions, thePythiumattacked young and old roots: and produced all the symptoms of the disease.7ThePythiumwas isolated again in the laboratory from inoculated plants.8This evidence demonstrates that thePythiumis capable of producing the strawberry disease as it occurs in field conditions. It is concluded thatPythiumis an important factor in exploiting the root system on which the general health of the plant depends.9The problem appears to be an agricultural rather than a mycological one. The main factor involved appears to be the general health of the plant. The fungal attack is to be regarded as an important accessory to the main Factor. It is, however, a factor which has become increasingly aggressive owing to the accentuation of certain soil conditions.10Experimental work on the soil is being carried out side by side with the mycological st

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1927.tb07075.x

出版商:Blackwell Publishing Ltd    

年代:1927

数据来源: WILEY

摘要:

Summary.1The “preferential food theory” as an explanation of the action of green manure in the control of scab is criticised.2Experiments are described in which potatoes are grown in series of pots containing soil only or soil mixed with grass cuttings. In each series the pots were inoculated with twoActinomycesspecies—the one,A. scabies(Thaxter) Güssow emend. M. and B., a virulent scab producer; the other,A. praecox, an obligate and prolific saprophyte. In Exp. 1, the inoculum ofA. scabieswas made to decrease and that ofA. praecoxto increase along the series. In Exps. 2 and 3 the inoculum ofA. scabieswas kept constant, and that ofA. praecoxwas gradually increased along the series of pots.3In the absence of the saprophyticActinomycesspecies, grass alone exerted no inhibitory action on scab.4A reduction of scab was obtained in all pots whether of soil or soil mixed with grass to which an inoculation ofA. praecoxhad been given. This reduction was most marked in the case of the maximum inoculation withA. praecox.5Counts of the twoActinomycesspecies were made from soil samples taken from the pots during and after growth of the potato crops, and from these it was found that the presence of the saprophytic species had exerted a very strong depressing effect upon the parasitic species. This depressing effect was most marked after a whole season's growth as shown by Exp. 3. Here, on the millionth dilution platings from a pot inoculated withA. scabiesalone, 225 colonies grew but no colonies of this species were found on the plates of the same dilution in the case of three pots to which inoculations ofA. praecoxhad also been given.6The inhibitory effect ofA. praecoxonA. scabiesis not due to the setting up of an unfavourable soil reaction but is probably caused by a starving out of the weaker organism in competition for the available food supply of the soil.7It is suggested that the beneficial effect of green manuring on scab under field conditions is due to similar competitive action and that in this competition the bacteria as well as theActinomycesmay play a part.8The cases in which green manuring has apparently failed to inhibit scab have been considered from this fresh point o

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1927.tb07076.x

出版商:Blackwell Publishing Ltd    

年代:1927

数据来源: WILEY

摘要:

Summary.1The toxicities toAphis rumicisof certain aliphatic and aromatic amines and of some of the simpler nitrogen‐heterocyclic derivatives have been quantitatively determined.2Tetramethylammonium hydrate and chloride are more toxic than the corresponding tetraethylammonium compounds. This is in keeping with the findings of Dale and his co‐workers who have shown that tetramethylammonium has certain physiological effects similar to those of nicotine which are not shown by tetraethylammonium.3The aromatic amines, on the whole, show little insecticidal action. Aniline and most of the aliphatic anilines are only slightly toxic toA. rumicis. The substitution of aromatic groups in the amino group of aniline increases toxicity more than the substitution of aliphatic groups. There are interesting relationships in regard to toxicity among these compounds. For example, the following orders of toxicity were noted:Phenylamine (aniline)triphenylamine.Phenylamine (aniline)dibenzylaniline.Benzylaminetribenzylamine.4o‐Nitraniline is one of the most toxic of the aniline derivatives.5α‐Naphthylamine is more toxic than aniline. Substitution of various radicals in the amino group of aniline has a greater effect on the toxicity of the resulting compound than substitution of the same radicals in α‐naphthylamine. α‐Naphthylamine derivatives are more toxic than the corresponding β‐derivatives.6Among the heterocyclic compounds, nicotine is highly poisonous toA. rumicis. The heterocyclic rings constituting the molecule of nicotine are much less toxic than nicotine itself; pyrrole and pyridine show comparatively slight insecticidal action. The order of toxicity of the simpler N‐heterocyclic compounds runs:Pyrrole

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1927.tb07077.x

出版商:Blackwell Publishing Ltd    

年代:1927

数据来源: WILEY

摘要:

Summary.Experiments on glasshouse fumigation with calcium cyanide in Great Britain during 1925–26 indicate that this material is a satisfactory source of hydrocyanic acid gas, and can be used to control a number of the usual pests infesting glasshouse plants.Trialeurodes vaporariorumWestw. was held in check with dosages of 1/12–1/5 oz. per 1000 cu. ft. and effectively controlled with dosages from 1/4–3/4 oz. per 1000 cu. ft. according to the conditions prevailing.At least six species of greenhouse aphides were controlled with dosages varying from 1/1 oz. to 1/2 oz. per 1000 cu. ft.Thrips, of which four species were dealt with, were more difficult to control, apparently only the adults being affected by the hydrocyanic acid gas. Dosages of 1/3 to 11/2ozs. per 1000 cu. ft. killed varying percentages of the adults and a series of fumigations were found to give satisfactory co

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1927.tb07078.x

出版商:Blackwell Publishing Ltd    

年代:1927

数据来源: WILEY

摘要:

Summary.1Experiments are described showing that it is possible to conduct laboratory experiments on micro‐organisms in stored soil, providing the surface of the soil is large relatively to its volume.2Experiments on the influence of moisture on the soil protozoa show that active forms are found in soils containing a very low per centage of water.3The flagellateCercomonas crassicaudawas found to excyst and reproduce in air‐dried soil brought to 1/6 the water‐holding capacity. The numbers of the bacteria also in this experiment nearly doubled their numbers in 24 hours.4Four common soil protozoa were found to behave normally in soil of 1/2 and 1/3 the water‐holding capacity, which previously had been air‐dried and then brought to the desired water content5Field soils having water contents of 6 per cent, in one case and 4 per cent. in another corroborated the laboratory experiments In all of these samples activeCercomonaswere found, other protozoa being present only in the form

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1927.tb07079.x

出版商:Blackwell Publishing Ltd    

年代:1927

数据来源: WILEY

摘要:

The Insects of Australia and New Zealand. By R. J. Tillyard.The Aspergilli. By CharlesThomand MargaretB. Church.Potato Varieties. By R. N. Salaman.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1927.tb07080.x

出版商:Blackwell Publishing Ltd    

年代:1927

数据来源: WILEY